CA1038571A - Attenuating melt-extruded filaments with converging non-symmetrical gas streams - Google Patents

Abstract

PROCESS AND APPARATUS FOR
PRODUCING FIBROUS STRUCTURES
;
ABSTRACT OF THE DISCLOSURE
Apparatus and method for producing filamentary material by extruding substantially axially through an orifice comprising contacting the extruded filament stream downstream of the orifice and prior to hardening with a plurality of converging, substan-tially planar, high velocity gas streams, each moving substantially in the direction of the filament stream such that they converge upon the filament stream at an angle of from about 45 to 5 degrees from the axis of the polymer extrusion nozzle. The planes of the gas streams intersect at a point which is at a distance measured perpendicularly from the axis of the extrudate stream at least equal to the diameter of the extrudate stream.

Description

BACKGROUND OF THE INVENTION
This invention relates to the production of filamentary material. It is particularly concerned wit`h novel apparatus and -process for spray spinning molten fiber-forming polymers to form nonwoven structures. ~ -Various proposals have been advanced heretofore in con-nection with integrated systems for forming fibrous assemblies, . ~ .
such as nonwoven fabrics and the like, directly from molten `-~
fiber-forming materials. In general, the previously proposed systems envisioned an extrusion operation followed by collection -.` `
of the extruded filamentary material in the form of a continuous fabric, web or other desired fibrous assembly. When details are considered, however, the various proposals differed in substantlal ways.
In recently issued U.S. Patent 3,543,332, a novel method for spray spinning molten fiber-forming polymers is ~ shown. Filamentary material is extruded substantially axially i~ through an orifice and contacted downstream prior to hardening by a plurality of high velocity gas streams, each moving in a direction having a major component in the direction of extrusion ~-I of the filament stream in a shallow angle of tangential con-! vergence therewith to attenuate the filament stream. The i' axes of the gas passages and corresponding gaseous streams :~ :
I are skewed about the extrusion orifice such that they are non-s ,/
intersecting axes spaced about the axis of the extrusion orifice.
' The present invention is concerned with an improved `;
3 method and apparatus for the direct production of filamentary materials. The present invention provides improved method and ~ 30 apparatus for spray spinning molten fiber-forming materials at j production rates much higher than the prior art processes. At ~ the same time, the invention produces a substantially uniform i - 2 -.; , ~3~
spray-spun fibrous structure while minimizing the formation of shot or ` .... . .
objectionably short fibers which detract from the desirability of ~he collected fibrous assembly.
This invention rclates to a process of producing a nonwoven self- :~
bonded structure of randomly arranged synthetic fibrous material comprising first extru~ing toward a collection surface a substantially continuous ~;.
filament-forming synthetic organic polylner material in liqùid phase at à :
filament stream under conditions to form a fibrous material, attenuating the extrudate utilizing a plurality of converging substantially planar gas streams all having the major force component in the direction of the filament stream, the planes of all the attenuating gas streams intersecting the axis :~
of the extrudate stream at an angle of from less than 45 degrees to more I than 5 degrees, the planes of all the gas streams intersecting each other ¦ at a point which is at a distance, B, measured perpendicularly from the ..
axis of the extrudate stream at least equal to the diameter of the extru-date stream at a point along the extrudate stream in juxtaposition to the point of intersection of the gas streams, the perpendicular distance, A, `.
from the extrusion nozzle to the point of intersection of the gas streams ~ :
being at least 2 inches, the fibrous material when it hits said collection ~0 surface being tacky and adhering to previous layers thereof and forming a self-bonded structure.
This invention also relates to apparatus for producing organic thermoplastic filamentary material comprising nozzle means having an extru- ~ ~:
sion orifice for fiber-forming material and a plurality of substantially ` rectangular gas outlet passages shaped so as to emit substantially planar ; .
.~ gas streams, said gas outlet passages being spaced from said extrusion `
orifice and separated from said nozzle means by an insulating means, said gas outlet passages being so positioned with respect to the nozzle means .
such that: 1) the gas passages are closer to the axis of the extrusion orifice at the outlet end of the passage than at an interior zone of the : ~.
passage so as to direct.the gas stream in a convergence angle with the axis of the extrusion orifice of from about 5 to 45 degrees, 2) no two of the :

ij ~
:i " .. . .. . . . .

'~ ~LOi;~S'f7~
planar projections of the gas outlet passages converge and intersect with the axis of the extrusion orifice at the same angle, and 3) planar projec~
; tions of the gas outlet passages intersect at a point which is at a , distance measured perpendicularly from the axis of the extrusion orifice ;~
f at least equal to the diameter of the extrudate stream at a point along the extrudate stream in juxtaposition to the point of intersection of the planar projections of the gas outlet passages, and means for supplying said gas passages with gas under pressure to be projected from said passag~s to .:
contact and attenuate the stream of fiber-forming material issuing from said extrusion orifice.
In accordance with an embodiment of the invention, spinning nozzle means are provided with an extrusion orifico for a ~iber-orming material and with a plurality of substantially rectangular gas outlet passages spaced apart from the extrusion orifice to supply jets of high velocity gas for attenuating the extruded filament stream prior to hardening of the filaments.
The molten polymer and attenuating gas do not flow through the same nozzle or other part of the spray-spinning equipment. The gas passages are separated from the extrusion orifice by an insulating means such as an air ~;
space. As a consequence, the gas flow, even if it is not heated, would cause only minimal heat transfer from the polymer to the gas. Such an air space eliminates the need for either heating the attenuating gas or heating the polymer to an excessively high degree above the required extrusion temperature such that the heat transfer would lower the polymer temperature only to the required extrusion temperature. The direction of the gas jets is such that substantial drag forces are applied to the extruded filament ~ stream in the direction of extrusion for attenuating or drawing the material '3 leaving the extrusion orifice. Further, the gas passages are positioned such that the planar gas streams are directed substantially in the direction of flow of the extrudate stream in such a manner that the gas streams con-verge upon the extrudate f :~

~f -3a-'i fl,,~
'.

~03~
o~ o~
strea~. The planes of ~hc gas streams ~ the planar projectiorls o~ the gas outlet p~sages intersect at ~ point which is at a distance measu~ed p~rp~l1dicul2rly from the axis of the extrudate stream at least equal to the diameter o 1:he ex~rudate stream.
S The planes of the attenuating gas streams contact the polymer extrudate stream at an angle of from about 45 to 5 degrees from the axis of the poIymer extrusion nozzle to project it away from the extrusion orifice.
Brie~ly, a relatively heavy monofil is extruded and a plu-rality of streams of gas, e.g., steam or air, are directed at a shallow angle in the direction of Elow of the freshly extrudea monofil. This attenuates the mono~il into relatively fine denier material and, like the more conventional dxawing, also increases the tenacity of the solidified extrudate. Depending upon~the lS conditions of extrusion, the filamentary material will be one or more substantially continuous structures, or relatively long ~ -staple fibers, or conventional length fibers, possibly mixed with varying amounts o solid debris or "shot".
The severity of the gas streams varies the attenuation and determines the denier of the resulting fibrous material which m~y range from about O.l up to about 50, although for maximum surface and strength the fiber denier is preferably mostly below about 25 denier. Actually each product will include a ' range of deniers which will add to its strength and performance.
¦ 25 The extrudate is discharged onto a suitable collection sur-fi f~ce such as a xotating collector drum. The height or length of ~ the resulting structure can be set by travexse or by use of multi-f ple side-by-side extruders whose ~spray patterns overlap. The duration of spray obviously controls the thickness of the ,.

~, .. . - ...... . . . . . . .
; ~ - -- - ?~

resulting structu~e~. Thë ~ Q~ ~ ~s1of extrusion and collection are such that each ne~ layer when deposited is sufficiently tacky so ~s to adhere to ~he preceding ]ayer so that the total structure will be shape-rctaining Wit~lOUt further treatment.
The filamen~-forming Irlaterial ma~ comprise any known suitable.
polymeric mat,~rial which is plasticizable, soluble or fusible. If soluble materials are used in conjunction with a solvent, the problem of solvent removal is encountered which, o~ course, is avoid,ed where fusible ma~erials are employed. Representative fusible materials include polyolefins such a~ homopolymers ~nd copolymers of ole~ins, e.y. e~hyleneZ and propylene, especially stereospecific or crystalline polyethylene and polypropylene~Z;
polyamides such as nylon 66, nylon 6, and the like; polyesters such as polyethyleneterephthalate; cellulose esters such as cellu-~,15 105e acetate, and especially the secondary triacetate; polyure- ;
thanes, polystyrene; polymers of vinylidene monomers such as vinyl chloride, vinyl acetate, vinylidene chloride, and especially acrylonitrile; and mixtures thereof.
I ~SCRIPq'ION OF 'r~E: ~RAWINGS
A more complete understanding of these and other features of the invention will be gailled from a consideration of the fol-lowing detailed description of an embodiment illustrated in the accompanying drawings in which:
FIG. 1 is a schematic illustration of an extrusion and col-lection apparatus in accordance with the present invention;
FIG. 2 is a schematic plan view of the extrusion apparatus ., .
and process in accordance with the present invention;
FIG. 3 is a graph illustratin~ vectorially the forces result-i ing from two converging planar gas streams;

~.03~
FIG. 4 is a schelllatic illustration showing Slow the vector force component illustrated in Figure 3 botll deflect and ~ccel-erate the filament stream.
FIG. 5 is a front elevation of one embodiment of an extrusion nozzle and planar attenuating gas jets usleful in the apparatus and process illustrated in Figure 2;
FIG. 6 is a schematic perspective illustration of an extru-sion nozzle having a pair of planar attenuating gas jets posi-tioned on each side of the extrusion nozzle;
FIG. 7 is a perspective view of a planar attenuating gas jet shown in Figure 6.
FIG. 8 is a schematic front elevation of the preferred ,1 1 , arrangement for utilizing our ex~rusion nozzles.
Referring now more particularly to the drawings, in Figure 1 lS a fiber-forming, thermoplastic polymer, pxeferably a polyolefin, ~l is fed to an extruder 10 provided with an adapter sect1on 12 to q which a gas, such as steam or air, is supplied. While extrusion temperatures may be anywhere above the melting point of the polymer, it has been found that best results are obtained by heating the .j .
ii 20 polymer to at least l50C., and preferably from about 250 to sJ about 350C. above the so~tening po~nt of the polymer beingextruded. For example, polypropylene having hereinafter defined characteristics will generally be heated to temperatures of from .
about 325 to about 400C. Polyethylene, on the other hand, will be heated to from about 350 to about 450C. A hot, molten stream of polymer 16 is discharged through a nozzle 14.
It is to be understood that nozzles having one or more ~;~ polymer orifices may be used. Also, a plurality of nozzles per collector may be employed. Elowever, there must be at least two planar gas streams per polymer orifice. The ~ttenuating gas ~ orifices 18 are of an elongated rectangular crosQ section, as ;, , .

. .
.

. ,' ~03857~L `
shown in Figurcs 5 and 6, to emit substantially pl~nar gas streams 17.
The gas streams 17 act on the polymel stream 16 in conver-gence region 20 to form an attenuated filclment 22 wherein it S cools and partially solidifies while moviny toward collection surface 24 on which it is collected as a cylindris:al structure 26. The collection surface 2~ is ordinarily rotated at a speed sufficient to provide a moving surface of from about 25 to about 125 feet per minute by a motor drive. Collection surface 24 is in surface contact with roller 28, which acts as an idler roll and whose bias against the mandrel can be adjusted; the extent of the bias will effect how tightly the tacky filament packs against previous layers on the cartridge 26. ~oth the collection surface 24 and the roller 28 are reciprocated laterally by a traversing mechanism 30 whose throw determines the shape of the cylinder; the throw may be of constant length or may change in the course of package ~!i build-up to prod~ce a particular shape as may be needed for accep-~ tance in a receptacle of predetermined corresponding shape.
,j ~`he force of the attenuating gas on the polymer stream causes the polymer to attenuate greatly, e.g., from 10 to 500 times, I based on diameter ratios, and possibly fibrillate to a slight degree to produce a substantially continuous fiber. Some turbu-lence and resultant whipping about of the po}ymer stream occurs.
~! Consequently, a generally random, stereo reticulate structure of fiber results as the material impinges on the col}ector. Since the polymer is still in a somewhat molten or tacky state when it ..i 3 strikes the collector, some sticking together occurs at the ! points where fiber intersects. For brevity, this sticking will l be referred to as interfiber bonding, although it is to be ;.`
, . . .
.i .

un~erstood tha~ ~his bolldillg will ord~narily result from an indivi~lual fib~r loopill~ ahout and stickin~ or bonding to its~lf.
For best results, the collection surace 24 should be from about 6 to about 98 inches, preferably 10 to 30 inches, from polymer exit nozzle 14. With greater distances the spray pattern is difficult to control and the resul~ant web tends to be non-uniform. Shorter distances result in a web wihich contains too great a quantity of "shot", i.e., beads of non-attenuated polymer, which undersirably affects subsequent processing, web uniformity ~;
and surfa~e area.
In Figure 2 there is schematically shown a top view of the apparatus o this invention. A plurality of conver~ing substan-tially planar gas streams 18 (corresponding substantially to planar projections o~ gas outle~ passages 17) i.ssue from sub-1 15 st.an~ially rec~angulàr gas outlet passages 17. The axis 19 I o the nozzle 14 corresponds to the direction in which the , polymer stream is extruded. The gas jets 17 are positioned along side the e~:trusion nozzle 14 in such a manner that- the gas strea~s 18 are directed substantially in the direction of flow o the polymer extrudate along the nozzle axis 19. The planes of the gas streams and planar projeations of tha gas outlet - ;
passages intersect at a point 21 wh$ch i8 at a distance B mea-I sured pexpendicularly from intersection point 21 to the nozzle I axis 19. The distance B is at least equal to the diameter of `! 25 the extrudate stream at a point 23 along the nozzle axis in juxtaposition to the point of intersection 21. Preferably B
is at least 0.06 inch, most preferably from about 0.2 to 2.0 inches. The point 23, which defines the perpendiculax distance from the nozzle 14 to the intersection point 21 is a distance A of at least 2.0 inches from the point of extrusion nozzle 14, preferably from about 2.5 to 7.0 inches. The attenuating '. gas jets 17 ar~ positioned along side the extrusion nozzle ;, -8 1: .

1~3~;t71 suoh that thc planes o the attenuating gas streams 18 intersect the no~ axis 19 (al50 ~he a~is of the extruda~e skream) at an angle (~1 and ~ 2) less than 45 degrees to more than about 5 degrees, preferably ~rom abou~ 10 to 40 degrees, to project the ; 5 extrudate stream away from the ex~rus~n nozzle.
In Fiqure 3 the force of the gas streams 18 are shown vec-torially. The Y force component i5 in the direction of the extru-sion nozzle axis and polymer extrudate stream, and serves to ac-celerate and attenuate the extrudate stream.
An~lesC~l and ~ 2~ shown in Fig. 2, are not the same so that the intcrsectioll point of the p}anes of the gas streams is of the nozzle axls and extrudate stream. Figur~ 4 shows that the eff~ct of this i5 to deflect the extrudate stLeaM 16, first to one side and then to the other, in addition to attenuatin~
~ ~ 15 the extrudate. If ~1 and ~2 ~e identical, the planar filament 3 streams 18 would intersect on the nozzle axis and substantially on the extrudate stream. As can be seen from the examples, this leads to much lower surface area when compared to the method of this invention illustrated in Figure 2. It is pxobable that the efect of the gas streams intersecting on the extrudate stream is to cut the stream and produce a less open, lower surface area product.
The illustrated extrusion nozz}e 14 has a center po}ymer exit orifice 15, as shown in Figure S, which ordinarily has a ~ 25 diame~er of from about 0.01 to about 0.10 inch, and preferab}y `l from about 0.015 to about 0.030 inch.

In the preferred embodiment, polymer is ~eneralLy extruded ~ through the nozzle at 1 to about 30 lb./hr., and desirably at `~} 5 to 15 lb./hr.
,;
:, _ g _ :
: ,,, - Along si~]e polyn~er exit orifice 15, as shown in Figures 5 and 6, are a plurali~y of a~t~nuating substantially rectangular eloncJated ~as orifices 1~ having a width of from about 0.002 to about 0.050 inch, preferably from about 0.004 to about 0.025 inch, and a length of at least about 0 5 inch, preferably from about l.0 to about 3.0 inches. Attenuat:ing ~as nozzles 18 emit ..
substantially planar gas streams 17 and are positioned, as illus-- trated in Figures 2 and 8.
Figures 6 and 7 show, in perspective, a preferred embodiment `~
1~ of a gas jet for èmitting a substantially planar gas stream. The gas enters through gas inlet passage 25 and is emitted through rectangular elongated gas orifice 18.
EX~MPLE l Isotactic polypropylene having an intrinsic viscosity of 1.5 and a melt flow rating of 30 is spray-spun at a melt tempera-., . . ~ , .
i ture of 390C. through four extrusion orifices arranged as shown ,. ~
in Figure 8. Each orifice is of a substantially circular cross-section having a diameter of about 0.016 inch. Referring to Figure 8, two planar attenuating gas jets, as shown in Figure 5, were spaced at a distance of 2 inches from the axls of each extrusion nozæle, in approximate.~y parallel relationship to each other along side each extrusion orifice. The elongated rectangu-lar air jets had an orifice width of 0.010 inch and a length of about 1.88 inches and each emitted ambient air flowing at a rate 'f o about 56 cubic ~feet per minute at a pressure of about 65 p.s.i.g.
Referring to Figure 2, the gas jets 17 are positioned so that the planes of gas streams 18 intersect at a point 21 which is at a distance B of 5~16 inch from the axis of the extrudate stream which corresponds to nozzle axis 19. The distance A which defines .~ --10--1~385i~7~
t}l~ ~istance from thc orifice 1~ to the inter.section point 21, is 4 inches. As a rcsult, ~he planes of the ~as ~treams intersect thc axis of the extr~dAte s~ream at angles ~Xi and C~f2 of a~,out 30 ~egrees an~ 25 degrees respectively. The polypropylene extru-S date is collectea on a metal drum having a diameter of 1 incll toproduce annular cylindrical structures. The total throughput of polypropylene lS a~out 6 lb./hr.
The procedure is repeated, except that the extruder through-put is increased such that the total throughput of polypropylene being spray spun is 9 lb./hr.

Polypropylene, as in ~xample 1, is spray spun throu~h one or more circular orifices, utilizing planar attenuating ~as jets, as shown in Figure 6, spaced at a distance of 2 inches from the 1~ axis of each extrusion orifice. The spray spun structure was collected on a cylindrical drum! The process conditions for 14 runs are cummariYed in Ta~le 1 below:

.
!
.1 ..

.

., , , .
;'`, --" ~ ~ . . . .

~) ~J ~ I l ~ 3E~
~ f ) r~l f~) D' ~ Ul f'~ `f~ f`~ 1 CO C~ fJO f'7 ) ~ ~r ~ f~ f~ f~ r ~ r ~n t,'' fi~ ~J . , , , . . . . , . . . . ~ ~
'.1 Ul ~ i'i fJ O O O O O O O f~ OO O O O O :
t~ -- a ." o o ^
t) ~
i-' ~ E' fJ O 1~ f~ Ul O O IJ'~ U') Il~ Ir) O O O O
~ ~, a) u ~ s . . . . . . . , . O
O ~ Q) ~ O ~D fO ~ f~ f~ f~ f~ f~ f,~
1 N ~1 r~
C~ O O
æ-J.

O _ f~) f~t f'7 f~ OO O O ' C1 ~ 0 ~,1 E-'i rl tJ~ _ O _ ., ~ ~r ~ f~l f,~ f,~ f,~l f,~l f,~ f,~l f~ ~ f~ t~ ~ f,~
~ . ., 0 1 o o o o 1~ t` fJO fJ~ ~ r f~ ~ o '~ ' . '~1 f~ f~1 f~ f~ f.~l f.~l f~) ~ f,'~ f" ~ f~ f~ f`": ' ' '' . . i~ . .
:: ~ tj ~ ~ ~ ~ a o ~ ~ o o o ~ o _ I ,^n .' a~
f~ ~ fit~ ~ ~ ~ ~ ,~p , _ . I . ~n ,n h ~ D ~o tJ~cnu~ c~ Ul G~ N N N f,~
..
rl t~ 1 o o o o It~
C ~ f~t~ t~ ~ f~
.,, p, : .
,, h 3i :: u~ n, ~ o o o o .~ o,~ ~n ,~n ,~n n ~ n ~n ,~n ,n ~ .
¢ ~ U
,~n ' -- - ', '', fJ`.-~
':i ~ 4 ~ -:j . 01 ~' ,f~
` O ~D ~ tn fJ U~ iD ~ 0 ~ D f.~Of.~ f,l ~ f~O
~" ~i lH ,~; U o O O o O f~ O O O O O O O O
h~
~1 O O ~f ~ O O O O O O O O O O O
-i: x o-a--;., ,~1 ... .
n. _ ~n ~ ~ ~ o o u~ ~n u~ ,n o o o o ;' .
:: ,f~ f~ ~ V ~t~ ~V ~ r~
O ~ N t`~t`l f.`J f,-~J f,~ ~ t~ f~ f,~
!
'':i : ... .. . . .

~3E~
The molccules in the surfac:e layer of a solicl are bound on onc side to i.nner mol&cul.es but there is an imbalance of atomic and molecular forccs on t:he other. The surface molecules attract gas, vapor, or liquid molecules in order to satisfy these latter fo~ces. The attraction may be either physical or cllemical, de-pending on the system i volved and the ternperature employed.
Physical adsorpti.on (f.requently referred to as van der Waal's adsorption) is the result of a relatively weak interaction between ~ .
a solid and a gas. l'his type of adsorption has one primary lO characteristic. Essentially all of a gas adsorbed can be removed by evacuation at the same ter.!perature at which it was adsorbed.
While the first gas molecules to contact a clean solid are held more or less rigidly by van der ~aal's forces, the forces active in the condensation of vapors become increasingly rcsponsi-ble for the binding energy in subsequent layer development. The ~, . .
expression Va = tn~

.~ where Va is the volume of gas adsorbed at pressure P, Vm the I volume adsox~e.d when the entire adsorbing surface is covered by a monomolecular layer, C a con~tant, and Ps the saturation pressure of the gas ~actually the vapor pressure at a given temperature , of a large quantity of gas condensed into A li~uid), is obtained '~. by equating the rate of condensation of gas molecules onto an adsorbed layer to the rate of evaporation from that layer and Z5 summing for an infinite number of layers. The e~pression des-. cribes the great majority of low temperature adsorption data.
; Physical measurements of the volume of gas adsorbed as a function of pressure at a fixed temperature, therefore, permit calculation ~ m~ thc volume of gas required to form a layer one rnoleculethick. Equation l can be rearranged to the linear fortn ~.03~
P = ~ C-1 ~ P
,, Va (P ~ P~ vmc ~VmCJ Ps ' Then a plot of data or P/Va(Ps - P~ vexsus P/PS ~ives a straight line, the int~rcept and slope of which are l/VmC and (C - l)VmC, r,nspectively. The value of Vm is thus readily extracted from a series of measurem-nts. From this information and knowledge of - the physical dimensions of single molecules, the surface area of ., the adsorbing solid is computed.
As shown in Table 1 above, surface area measurements were taken utilizing Orr Surface - Are~ Pore - Volume Analyzer (Model .~, 2100A). The runs using the pr~ferred process of ~his invention ~2, 2a, 2b, 2c, 2, 2g, 2k and 2m) exhibited a higher surface area than the runs wherein the attenuating gas streams intersected .,j ~.
on the axis of the extrudate stream. A direct comparison can be ~ between runs 2f and 2h, 2g and 2i, 2j and 2k, and 21 and 2m.
,.
Increases in surface area of from 0.05 to 0.17 meters2/gram are ;J achieved.
The higher the surface area, the greater the filtration ,,~ .
efficiency of the structure.
he preferred fiber-forming polymers employed in the present inv~ntion are the polyolefins, such as polyethylene or polypropy~
lene. The melt index of the polyolefin prior to extxusion will ordinarily be from about 5 to 60 and preferably from about 15 to `~ 40. The intrinsic viscosity will be from about 1.0 to about 2.5 and preferably from about 1.0 to about 2Ø
Inste2d of the polyolefins, one may also employ other thermo-plastic, melt-extrudable, fiber-forming polymers such as poly-amides, polyesters, phenol-formaldehyde resins, polyacetals, and cellulose esters, e.g., cellulose acetate. With some of the poly-i~ mers, spray spinning is aided by mixing the polymer with a melt ,' 30 depressarlt to facili~ate melting without decomposition,. 14 :~L03~
Alr will normally be employed as the at~enuating gas for reasons of economy. Other gases, e.g., steam, nitrogen, heli~m, etc., are also suitable. Usually, the attenuating gas will be at ambient temperature. Iieated gas, e.g.; at a temperature of 250 to 500~C., may also be advantageously used, however.
It will be appreciated that the instant specification and examples are set forth by way of illustration and not limitati~n, and that various modifications and changes may be made without departing fLom the spirit and scope of the present invention.

. ' , .
, .

, ~
~ .

`
1~

-i,..

.~ , ~ . , . , , ,, , , ~ ~, .

Claims (5)

WHAT IS CLAIMED IS:

1. The process of producing a nonwoven self-bonded structure of randomly arranged synthetic fibrous material comprising first extruding toward a collection surface a substantially continuous filament-forming synthetic organic polymer material in liquid phase at a filament stream under conditions to form a fibrous material r attenuating the extru-date utilizing a plurality of converging substantially planar gas streams all having the major force component in the direc-tion of the filament stream, the planes of all the attenuating gas streams intersecting the axis of the extrudate stream at an angle of from less than 45 degrees to more than 5 degrees, the planes of all the gas streams intersecting each other at a point which is at a distance, B, measured perpendicularly from the axis of the extrudate stream at least equal to the diameter of the extrudate stream at a point along the extrudate stream in juxtaposition to the point of inter-section of the gas streams, the perpendicular distance, A, from the extrusion nozzle to the point of intersection of the gas streams being at least 2 inches, the fibrous material when it hits said collection surface being tacky and adhering to pre-vious layers thereof and forming a self-bonded structure.

2. The process of claim 1 wherein the collection surface is positioned at a distance of from about 6 to 48 inches from the polymer extrusion nozzle.

3. The process of claim 1 wherein the distance A ranges from 2 to 7 inches.

4. The process of claim 1 wherein the angle of intersection of the gas streams is from 10 degrees to 40 degrees.

5. Apparatus for producing organic thermoplastic fila-mentary material comprising nozzle means having an extrusion orifice for fiber-forming material and a plurality of substan-tially rectangular gas outlet passages shaped so as to emit substantially planar gas streams, said gas outlet passages being spaced from said extrusion orifice and separated from said nozzle means by an insulating means, said gas outlet passages being so positioned with respect to the nozzle means such that: 1) the gas passages are closer to the axis of the extrusion orifice at the outlet end of the passage than at an interior zone of the passage so as to direct the gas stream in a convergence angle with the axis of the extrusion orifice of from about 5 to 45 degrees, 2) no two of the planar projec-tions of the gas outlet passages converge and intersect with the axis of the extrusion orifice at the same angle, and 3) planar projections of the gas outlet passages intersect at a point which is at a distance measured perpendicularly from the axis of the extrusion orifice at least equal to the diameter of the extrudate stream at a point along the extrudate stream in juxtaposition to the point of intersection of the planar pro-jections of the gas outlet passages, and means for supplying said gas passages with gas under pressure to be projected from said passages to contact and attenuate the stream of fiber-forming material issuing from said extrusion orifice.